Gas separation is important in many industries for removing undesirable contaminants from a gas stream and for achieving a desired gas composition. For example, natural gas from many gas fields can contain significant levels of H2O, SO2, H2S, CO2, N2, mercaptans, and/or heavy hydrocarbons that have to be removed to various degrees before the gas can be transported to market. It is preferred that as much of the acid gases H2S and CO2 be removed from natural gas as possible to leave methane as the recovered component. Natural gas containing a high concentration of CO2 should not be directly introduced into pipelines because it may be corrosive to the pipelines in the presence of water. Furthermore, small increases in recovery of methane can result in significant improvements in process economics and also serve to prevent unwanted resource loss. It is desirable to recover more than 80 vol %, particularly more than 90 vol %, of the methane when detrimental impurities are removed.
Additionally, synthesis gas (syngas) typically requires removal and separation of various components before it can be used in fuel, chemical and power applications because all of these applications have a specification of the exact composition of the syngas required for the process. As produced, syngas can contain at least CO and H2. Other molecular components in syngas can be CH4, CO2, H2S, H2O, N2, and combinations thereof. Minority (or trace) components in the gas can include hydrocarbons, NH3, NOx, and the like, and combinations thereof. In almost all applications, most of the H2S should typically be removed from the syngas before it can be used, and, in many applications, it can be desirable to remove much of the CO2.
Adsorptive gas separation techniques are common in various industries using solid sorbent materials such as activated charcoal or a porous solid oxide such as alumina, silica-alumina, silica, or a crystalline zeolite. The selection of suitable zeolite materials is critical for CO2 capture and separation. However, a significant challenge exists in arriving at suitable materials because of the large diversity of zeolite compositions. For example, there are approximately 220 zeolite topologies recognized by the International Zeolite Society, which may have varying Si/Al ratios as well as varying cation concentrations resulting in numerous possible zeolite materials. Thus, there is not only a need for zeolite materials with improved adsorption capacity for a gas contaminant, such as CO2, which can be used in various gas separation processes but also a need for improved methods for identifying suitable zeolite materials for CO2 adsorption.